Self-emulsifying aqueous polyurethane dispersions

ABSTRACT

Self-emulsifying aqueous primary dispersions comprising polyurethane, processes for their preparation, and their use.

The present invention relates to self-emulsifying aqueous primarydispersions which comprise polyurethane. The present invention alsorelates to a process for preparing these primary dispersions, and totheir use.

From the prior art it is known that ionic polyurethane dispersions aresuitable for paints, impregnating systems, and coatings for textile,paper, leather, and plastics. Numerous aqueous polyurethane adhesives aswell are known. The ionic group here not only contributes todispersibility in water but is also an important constituent of theformula for the purpose of producing ionic interactions which influencethe mechanical properties. Preparation in the case of this prior arttakes place by the acetone process or prepolymer mixing process.

A disadvantage is that such processes are inconvenient and expensive,especially when solvents are used. Moreover, the reagents used tointroduce the hydrophilic groups are expensive specialty chemicals.

German laid-open specification DE-A1 198 25 453 describes, for example,dispersions which comprise polyurethanes. The polyurethanes in questionare what are known as self-dispersible polyurethanes, whoseself-dispersibility is achieved through incorporation of ionically ornonionically hydrophilic groups. These dispersions are used toimpregnate synthetic leather.

From WO 00/29465 it is known that it is possible to react isocyanate andhydroxyl compound in aqueous miniemulsions to form polyurethanes. Thereis, however, no description of compositions which would make it possibleto prepare aqueous coatings or adhesives.

WO 02/64657 describes PU minidispersions containing certain diols, withwhich a reaction to polyurethane can be achieved without theintermediate step of preparing a prepolymer. The compositions describedtherein, however, do not meet the dispersibility requirements.

Also known from the prior art are polyurethane coating materials withouthydrophilic groups, with or without solvent. These materials, however,have disadvantages in comparison to the dispersions described. Accountmust be taken in particular of the environmental problems arising fromthe use of solvents or free isocyanate. A further disadvantage are themolar masses, which are lower than those of the dispersions. Furtherstill, the reaction of isocyanate in an aqueous environment is alwaysaccompanied by losses due to formation of urea, which make it impossibledirectly to adopt known formulas for a hydrophobic polyurethane.

It is an object of the present invention to provide primary dispersionswhich comprise polyurethane, which are finely divided without the use ofhigh shear forces, and which make it possible not only for the rawmaterials to be emulsified finely but also for the products to bedispersed.

We have found that this object is achieved by means of an aqueousprimary dispersion comprising at least one polyurethane obtainable byreacting

-   a) at least one polyisocyanate,-   b1) at least one polyol containing the structural unit    —[—CH₂—CH₂—O—]— one or more times,-   b2) if appropriate at least one polyol other than b1),-   b3) if appropriate at least one compound containing at least two    isocyanate-reactive groups selected from thiol groups and primary    and secondary amino groups,-   b4) if appropriate at least one monofunctional monomer having an    isocyanate-reactive group, and-   c) if appropriate at least one ionic or potentially ionic synthesis    component,    wherein    the fraction of the structural units —[—CH₂—CH₂—O—]—, calculated at    42 g/mol, in the polyol b1) is from 10 to 90% by weight and    in the sum of the components a)+b1)+b2)+b3)+b4)+c) is at least 3% by    weight.

In one preferred embodiment of the invention the ratio of isocyanategroups (a) to isocyanate-reactive groups (b) is from 0.8:1 to 3:1,preferably from 0.9:1 to 1.5:1, more preferably 1:1.

Examples of suitable components a) include aliphatic, aromatic, andcycloaliphatic diisocyanates and polyisocyanates having an NCOfunctionality of at least 1.8, preferably from 1.8 to 5, and morepreferably from 2 to 4, and also their isocyanurates, biurets,allophanates, and uretdiones.

The diisocyanates are preferably isocyanates having 4 to 20 carbonatoms. Examples of suitable diisocyanates are aliphatic diisocyanatessuch as tetramethylene diisocyanate, hexamethylene diisocyanate(1,6-diisocyanatohexane), octamethylene diisocyanate, decamethylenediisocyanate, dodecamethylene diisocyanate, tetradecamethylenediisocyanate, derivatives of lysine diisocyanate, tetramethylxylylenediisocyanate, trimethylhexane diisocyanate or tetramethylhexanediisocyanate, cycloaliphatic diisocyanates such as 1,4-, 1,3- or1,2-diisocyanatocyclohexane, 4,4′- or2,4′-di(isocyanatocyclohexyl)methane,1-isocyanato-3,3,5-trimethyl-5-(isocyanatomethyl)cyclohexane (isophoronediisocyanate), 1,3- or 1,4-bis(isocyanatomethyl)cyclohexane or 2,4- or2,6-diisocyanato-1-methylcyclohexane, and aromatic diisocyanates such as2,4- or 2,6-tolylene diisocyanate and the isomer mixtures thereof, m- orp-xylylene diisocyanate, 2,4′- or 4,4′-diisocyanatodiphenylmethane andthe isomer mixtures thereof, 1,3- or 1,4-phenylene diisocyanate,1-chloro-2,4-phenylene diisocyanate, 1,5-naphthylene diisocyanate,diphenylene 4,4′-diisocyanate, 4,4′-diisocyanato-3,3′-dimethylbiphenyl,3-methyldiphenylmethane 4,4′-diisocyanate, tetramethylxylylenediisocyanate, 1,4-diisocyanatobenzene or diphenyl ether4,4′-diisocyanate.

Mixtures of said diisocyanates may also be present.

Preference is given to aliphatic and cycloaliphatic diisocyanates, andparticular preference to isophorone diisocyanate, tetramethylxylylenediisocyanate (m-TMXDI), and 1, 1-methylenebis[4-isocyanato]cyclohexane(H₁₂MDI).

Suitable polyisocyanates include polyisocyanates comprising isocyanurategroups, uretdione diisocyanates, polyisocyanates containing biuretgroups, polyisocyanates comprising urethane groups or allophanategroups, polyisocyanates comprising oxadiazinetrione groups,uretonimine-modified polyisocyanates of linear or branchedC₄-C₂₀-alkylene diisocyanates, cycloaliphatic diisocyanates having 6 to20 carbon atoms in all or aromatic diisocyanates having 8 to 20 carbonatoms in all, or mixtures thereof.

The diisocyanates and polyisocyanates which can be used preferably havean isocyanate group (calculated as NCO, molecular weight=42) content offrom 10 to 60% by weight based on the diisocyanate and polyisocyanate(mixture), more preferably from 15 to 60% by weight, and very preferablyfrom 20 to 55% by weight.

Preference is given to aliphatic and/or cycloaliphatic diisocyanates andpolyisocyanates, examples being the abovementioned aliphatic andcycloaliphatic diisocyanates, respectively, or mixtures thereof.

Preference extends to

-   1) Polyisocyanates containing isocyanurate groups and formed from    aromatic, aliphatic and/or cycloaliphatic diisocyanates. Particular    preference is given here to the corresponding aliphatic and/or    cycloaliphatic isocyanato-isocyanurates and, in particular, to those    based on hexamethylene diisocyanate and isophorone diisocyanate. The    isocyanurates present are, in particular, trisisocyanatoalkyl or    trisisocyanatocycloalkyl isocyanurates, which represent cyclic    trimers of the diisocyanates, or are mixtures with their higher    homologs comprising more than one isocyanurate ring. The    isocyariato-isocyanurates generally have an NCO content of from 10    to 30% by weight, in particular from 15 to 25% by weight, and an    average NCO functionality of from 3 to 4.5.-   2) Uretdione diisocyanates having aromatically, aliphatically and/or    cycloaliphatically attached isocyanate groups, preferably    aliphatically and/or cycloaliphatically attached isocyanate groups,    and especially those derived from hexamethylene diisocyanate or    isophorone diisocyanate. Uretdione diisocyanates are cyclic    dimerization products of diisocyanates.

In the formulations of the invention the uretdione diisocyanates can beused as sole component or in a mixture with other polyisocyanates,especially those specified under 1).

-   3) Polyisocyanates containing biuret groups and having aromatically,    cycloaliphatically or aliphatically attached, preferably    cycloaliphatically or aliphatically attached, isocyanate groups,    especially tris(6-isocyanatohexyl)biuret or its mixtures with its    higher homologs. These polyisocyanates containing biuret groups    generally have an NCO content of from 18 to 22% by weight and an    average NCO functionality of from 3 to 4.5.-   4) Polyisocyanates containing urethane and/or allophanate groups and    having aromatically, aliphatically or cycloaliphatically attached,    preferably aliphatically or cycloaliphatically attached, isocyanate    groups, as obtainable for example by reacting excess amounts of    hexamethylene diisocyanate or of isophorone diisocyanate with    polyhydric alcohols such as trimethylolpropane, neopentyl glycol,    pentaerythritol, 1,4-butanediol, 1,6-hexanediol, 1,3-propanediol,    ethylene glycol, diethylene glycol, glycerol, 1,2-dihydroxypropane    or mixtures thereof. These polyisocyanates containing urethane    and/or allophanate groups generally have an NCO content of from 12    to 20% by weight and an average NCO functionality of from 2.5 to 3.-   5) Polyisocyanates comprising oxadiazinetrione groups, preferably    derived from hexamethylene diisocyanate or isophorone diisocyanate.    Polyisocyanates of this kind comprising oxadiazinetrione groups can    be prepared from diisocyanate and carbon dioxide.-   6) Uretonimine-modified polyisocyanates.

The polyisocyanates 1) to 6) can be used in a mixture, including ifappropriate in a mixture with diisocyanates.

Compounds used as reaction partners of the polyisocyanates a) arecompounds b) having isocyanate-reactive groups, which in accordance withthe invention are subdivided into compounds b1) to b4), with b2), b3),and b4) being optional.

Examples of suitable isocyanate-reactive groups are hydroxyl groups,thiol groups, and primary and secondary amino groups. It is preferred touse hydroxyl-containing compounds or monomers, b1) and if appropriateb2). In addition it is also possible to use compounds b3), which have atleast two isocyanate-reactive groups, selected from thiol groups andprimary and secondary amino groups.

Suitable compounds b1) are those polyols containing structural unit—[—CH₂—CH₂—O—]_(w)— one or more times, the fraction of the structuralunits —[—CH₂—CH₂—O—]—, calculated at 42 g/mol, in the polyol b1)accounting for a weight fraction of from 10 to 90% by weight, preferablyfrom 10 to 50% by weight, and more preferably 12-35% by weight.

The index w is a positive integer from 1 to 200, preferably from 2 to200, more preferably from 5 to 100, very preferably from 10 to 100, andin particular from 20 to 50.

The compounds b1) preferably have a molar weight of at least 500 g/mol,more preferably from 800 to 5000 g/mol.

The polyols b1) are preferably polyols with mixed alkoxylation, in whicha suitable starter molecule is alkoxylated with ethylene oxide and withat least one further alkylene oxide.

Examples of starter molecules include water, neopentyl glycol, neopentylglycol hydroxypivalate, 2-ethyl-1,3-propanediol,2-methyl-1,3-propanediol, 3-ethyl-1,5-pentanediol,3-methyl-1,5-pentanediol, 2-ethyl-1,3-hexanediol,2,4-diethyloctane-1,3-diol, hydroquinone, bisphenol A, bisphenol F,bisphenol B, bisphenol S, 2,2-bis(4-hydroxycyclohexyl)propane, 1,1-,1,2-, 1,3-, and 1,4-cyclohexanedimethanol, 1,2-, 1,3- or1,4-cyclohexanediol, 1,2-propanediol, ethylene glycol,2,2-dimethyl-1,2-ethanediol, 1,3-propanediol, 1,2-butanediol,1,3-butanediol, 1,4-butanediol, 1,6-hexanediol, 1,8-octanediol,trimethylolbutane, trimethylolpropane, trimethylolethane,pentaerythritol, glycerol, ditrimethylolpropane, dipentaerythritol,sorbitol, mannitol, diglycerol, threitol, erythritol, adonitol(ribitol), arabitol (lyxitol), xylitol, dulcitol (galactitol), maltitolor isomalt.

Examples of alkylene oxides are propylene oxide, isobutylene oxide,vinyloxirane and/or styrene oxide, preference being given to propyleneoxide and/or isobutylene oxide and particular preference to propyleneoxide.

Also suitable are glycidyl ethers of aliphatic or aromatic polyols.Products of this kind are available commercially in large numbers.Particular preference is given to polyglycidyl compounds of thebisphenol A, F or B type, their fully hydrogenated derivatives, andglycidyl ethers of polyhydric alcohols, e.g., of 1,4-butanediol,1,4-cyclohexanedimethanol, neopentyl glycol, of 1,6-hexanediol, ofglycerol, trimethylol-propane, and of pentaerythritol. Examples ofpolyepoxide compounds of this kind are Epikote® 812 (epoxide value:about 0.67 mol/100 g) and Epikote® 828 (epoxide value: about 0.53mol/100 g), Epikote® 1001, Epikote® 1007 and Epikote® 162 (epoxidevalue: about 0.61 mol/100 g) from Resolution Performance Products,Rütapox® 0162 (epoxide value: about 0.58 mol/100 g), Rütapox® 0164(epoxide value: about 0.53 mol/100 g), and Rütapox® 0165 (epoxide value:about 0.48 mol/100 g) from Bakelite AG, and Araldit® DY 0397 (epoxidevalue: about 0.83 mol/100 g) from Vantico AG.

Preference is given to bisphenol A diglycidyl ether, 1,4-butanedioldiglycidyl ether, trimethylolpropane triglycidyl ether, andpentaerythritol tetraglycidyl ether.

The alkylene oxides can be used in a mixture in the alkoxylation, soforming a random copolymer, or, preferably, the straight alkylene oxidescan be used in succession, so forming a block copolymer. Particularpreference is given to a block copolymer in which ethylene oxide is usedas the final alkoxylation step, so that the polyol b1) has at least oneprimary alcohol group as a terminal structural unit —CH₂—O—H, and withvery particular preference has two such terminal structural units.

The polyols b1) can also comprise polyesterpolyols obtained by reactingat least one dihydric or polyhydric alcohol with at least one dibasic orpolybasic carboxylic acid. Instead of the free polycarboxylic acids itis also possible to use the corresponding polycarboxylic anhydrides orcorresponding polycarboxylic esters of lower alcohols or mixturesthereof to prepare the polyesterpolyols.

The polycarboxylic acids can be aliphatic, cycloaliphatic, araliphatic,aromatic or heterocyclic and can be substituted, if appropriate, byhalogen atoms, for example, and/or can be unsaturated.

Examples thereof that may be mentioned include the following: subericacid, azelaic acid, phthalic acid, isophthalic acid, sodiumsulfoisophthalic acid, phthalic anhydride, tetrahydrophthalic anhydride,hexahydrophthalic anhydride, tetrachlorophthalic anhydride,endomethylenetetrahydrophthalic anhydride, glutaric anhydride, maleicacid, maleic anhydride, alkenylsuccinic acid, fumaric acid, and dimericfatty acids. Preference is given to dicarboxylic acids of the generalformula HOOC—(CH₂)_(y)—COOH, where y is a number from 1 to 20,preferably an even number from 2 to 20, e.g., succinic acid, adipicacid, dodecanedicarboxylic acid, and sebacic acid.

Examples of suitable polyols for preparing the polyesterol includeethylene glycol, propane-1,2-diol, propane-1,3-diol, butane-1,3-diol,butane-1,4-diol, butene-1,4-diol, butyne-1,4-diol, pentane-1,5-diol,neopentyl glycol, bis(hydroxymethyl)cyclohexane such as1,4-bis(hydroxymethyl)cyclohexane, 2-methylpropane-1,3-diol,methylpentanediols, and also diethylene glycol, triethylene glycol,tetraethylene glycol, polyethylene glycol, dipropylene glycol,polypropylene glycol, dibutylene glycol, and polybutylene glycols.Preference is given to alcohols of the general formula HO—(CH₂)_(x)—OH,where x is a number from 1 to 20, preferably an even number from 2 to20. Examples include ethylene glycol, butane-1,4-diol, hexane-1,6-diol,octane-1,8-diol, and dodecane-1,12-diol. Preference extends to neopentylglycol and pentane-1,5-diol.

In order in accordance with the invention to incorporate at least onestructural unit —[—CH₂—CH₂—O—]— into the polyesterol it is necessary forat least one synthesis component of the polyesterol to be ethyleneglycol, a polyethylene glycol having a molar mass of between 106 and2000, preferably between 106 and 1000, and more preferably between 106and 500, or an above-described copolymer of ethylene oxide with anotheralkylene oxide.

Also suitable are lactone-based polyesterdiols, which are homopolymersor copolymers of lactones, preferably hydroxyl-terminated adducts oflactones with suitable difunctional starter molecules. Suitable lactonesinclude preferably those derived from compounds of the general formulaHO—(CH₂)_(z)—COOH, where z is a number from 1 to 20 and where onehydrogen atom of a methylene unit may also have been substituted by a C₁to C₄ alkyl radical. Examples are epsilon-caprolactone, β-propiolactone,γ-butyrolactone and/or methyl-epsilon-caprolactone, and also mixturesthereof.

Examples of suitable starter components are the low molecular massdihydric alcohols specified above as a synthesis component for thepolyesterpolyols. The corresponding polymers of ε-caprolactone areparticularly preferred. Lower polyesterdiols or polyetherdiols as wellcan be used as starters for preparing the lactone polymers. Instead ofthe polymers of lactones it is also possible to use the corresponding,chemically equivalent polycondensates of the hydroxycarboxylic acidscorresponding to the lactones.

Suitable polyols b2) include all known alcohols with a functionality oftwo or more, provided they do not fall into the above list of thepolyols b1). The polyols b2) can, accordingly, also have a molar weightlower than 500 g/mol and a fraction of the structural units—[—CH₂—CH₂—O—]—, calculated at 42 g/mol, of less than 10% or more than90% by weight.

Examples are polyTHF having a molar mass of between 162 and 1458,poly-1,3-propanediol having a molar mass of between 134 and 1178,poly-1,2-propanediol having a molar mass of between 134 and 1178,trimethylolbutane, trimethylolpropane, trimethylolethane, glycerol,ditrimethylolpropane, dipentaerythritol, sorbitol, mannitol, diglycerol,threitol, erythritol, adonitol (ribitol), arabitol (lyxitol), xylitol,dulcitol (galactitol), maltitol, isomalt, and polyesterols andpolyetherols based thereon.

Likewise possible are polyesters formed from starting materials asmentioned above. It is also possible to use polyols based onOH-functionalized polybutadienes, polyacrylates, polysiloxanes, andpolycarbonates as monomers b2).

The fraction of the structural units —[—CH₂—CH₂—O—]—, calculated at 42g/mol, in the sum of the components a)+b1)+b2)+b3)+b4)+c) is inaccordance with the invention at least 3% by weight, preferably at least5% by weight, and more preferably at least 7.5% by weight. In generalthe fraction is not more than 90% by weight, preferably not more than75% by weight, and more preferably not more than 50% by weight.

Examples of suitable monomers b3) are hydrazine, hydrazine hydrate,ethylenediamine, propylenediamine, diethylenetriamine,dipropylenetriamine, isophoronediamine, 1,4-cyclohexyldiamine,piperazine or thiols such as 1,2-ethanethiol.

In minor amounts it is also possible to use monofunctional monomers b4)having an isocyanate-reactive group. Their fraction should not exceed 10mol % relative to NCO groups in component a).

Examples of b4) are methanol, ethanol, isopropanol, n-propanol,n-butanol, isobutanol, sec-butanol, tert-butanol, ethylene glycolmonomethyl ether, ethylene glycol monoethyl ether, 1,3-propanediolmonomethyl ether, n-hexanol, n-heptanol, n-octanol, n-decanol,n-dodecanol (lauryl alcohol), and 2-ethylhexanol.

Furthermore it is also possible for at least one ionic or potentiallyionic synthesis component c) to be present. Preferably, however, thepolyurethanes of the dispersions of the invention are synthesizedwithout components c).

Suitable components c) are compounds of at least one isocyanate-reactivegroup and at least one actively dispersing group.

Such compounds are represented, for example, by the general formulaRG-R¹-DGwhere

-   RG is at least one isocyanate-reactive group,-   DG is at least one actively dispersing group, and-   R¹ is an aliphatic, cycloaliphatic or aromatic radical comprising 1    to 20 carbon atoms.

Examples of RG are —OH, —SH, —NH₂ or —NHR², where R² can be methyl,ethyl, isopropyl, n-propyl, n-butyl, isobutyl, sec-butyl, tert-butyl,cyclopentyl or cyclohexyl.

With preference component c) is, for example, mercaptoacetic acid,mercaptopropionic acid, thiolactic acid, mercaptosuccinic acid, glycine,iminodiacetic acid, sarcosine, alanine, β-alanine, leucine, isoleucine,aminobutyric acid, hydroxyacetic acid, hydroxypivalic acid, lactic acid,hydroxysuccinic acid, hydroxydecanoic acid, dimethylolpropionic acid,dimethylolbutyric acid, ethylenediaminetriacetic acid, hydroxydodecanoicacid, hydroxyhexadecanoic acid, 12-hydroxystearic acid,aminonaphthalinecarboxylic acid, hydroxyethanesulfonic acid,hydroxypropanesulfonic acid, mercaptoethanesulfonic acid,mercaptopropanesulfonic acid, aminomethanesulfonic acid, taurine,aminopropanesulfonic acid, and the alkali metal, alkaline earth metal orammonium salts of these acids, and, with particular preference, theaforementioned monohydroxycarboxylic and monohydroxysulfonic acids andalso monoaminocarboxylic and monoaminosulfonic acids.

To prepare the dispersion the aforementioned acids, if not already insalt form, are fully or partly neutralized, preferably with alkali metalsalts or amines, tertiary amines for preference.

The dispersion of the invention is prepared by means of emulsionpolymerization.

Generally in these processes, in a first step, a mixture is preparedfrom the monomers a) and b) and also, if appropriate, c), the requiredamount of emulsifiers and/or protective colloid, hydrophobic additive,if appropriate, and water, and an emulsion is produced from saidmixture.

Preferably, in a first step, the organic phase is prepared homogeneouslyand in a second step this organic phase is added to a water phase orelse a water phase is added to the organic phase thus prepared.

With equal preference it is possible to introduce a portion of thesynthesis components to start with and to meter in the remainingportion. Preferably the synthesis components a) and those having a molarweight of more than 500 g/mol are introduced initially and the remainingsynthesis components are added; with particular preference the synthesiscomponents b1) can be introduced initially and the remaining synthesiscomponents added.

In accordance with the invention the average particle size (z-average)in the dispersion thus prepared, as measured by dynamic light scatteringwith the Malvern® Autosizer 2 C, is generally <1000 nm, preferably <500nm, and with particular preference <100 nm. Normally the diameter isfrom 20 to 80 nm.

In order to produce the emulsion it is necessary, in accordance with theinvention, to deploy an energy of not more than 10⁸ W/m³.

It is advantageous to carry out the preparation of the emulsion withsufficient rapidity that the emulsifying time is small in comparison tothe reaction time of the monomers with one another and with water.

In one preferred embodiment of the process of the invention the entiretyof the emulsion is prepared with cooling at temperatures below roomtemperature. Preparation of the emulsion is preferably accomplishedwithin a time of less than 10 minutes. Raising the temperature of theemulsion with stirring completes the conversion. The reactiontemperatures are situated between room temperature and 120° C.,preferably between 60° C. and 100° C. If necessary it is possible toapply pressure in order to keep low-boiling components liquid.

When producing emulsions it is general practice to use ionic and/ornonionic emulsifiers and/or protective colloids or stabilizers assurface-active compounds.

A detailed description of suitable protective colloids can be found inHouben-Weyl, Methoden der organischen Chemie, volume XIV/1,Makromolekulare Stoffe [Macromolecular compounds], Georg-Thieme-Verlag,Stuttgart, 1961, pp. 411 to 420. Suitable emulsifiers include anionic,cationic, and nonionic emulsifiers. As accompanying surface-activesubstances it is preferred to use exclusively emulsifiers, whosemolecular weights, unlike those of the protective colloids, are usuallybelow 2000 g/mol. Where mixtures of surface-active substances are usedit will be appreciated that the individual components must be compatiblewith one another, something which in case of doubt can be checked bymeans of a few simple preliminary tests. It is preferred to use anionicand nonionic emulsifiers as surface-active substances. Customaryaccompanying emulsifiers are, for example, ethoxylated fatty alcohols(EO units: 3 to 50, alkyl: C₈ to C₃₆), ethoxylated mono-, di-, andtri-alkylphenols (EO units: 3 to 50, alkyl: C₄ to C₉), alkali metalsalts of dialkyl esters of sulfosuccinic acid, and alkali metal saltsand/or ammonium salts of alkyl sulfates (alkyl: C₈ to C₁₂), ofethoxylated alkanols (EO units: 4 to 30, C₉), of alkylsulfonic acids(alkyl: C₁₂ to C₁₈), and of alkylarsulfonic acids (alkyl: C₉ to C₁₈).

Suitable emulsifiers can also be found in Houben-Weyl, Methoden derorganischen Chemie, volume 14/1, Makromolekulare Stoffe, Georg ThiemeVerlag, Stuttgart, 1961, pages 192 to 208.

Examples of emulsifier tradenames include Dowfax® 2 A1 from Dow, Emulan®NP 50, Emulan® OG, Emulsifier 825, and Emulsifier 825 S, Nekanil® 904 Sfrom BASF, Texapon® NSO from Henkel Corporation, Lumiten® 1-RA andLumiten E 3065 from BASF, Dextrol® OC 50 from AVEBE GmbH, Steinapol NLSfrom Goldschmidt REWO GmbH, etc.

Based on the amount of monomers present in the aqueous emulsion thisquantity of emulsifiers is generally in the range from 0.1 to 10% byweight. As already mentioned it is possible to add protective colloidsto the emulsifiers at the side, these protective colloids having thecapacity to stabilize the disperse distribution of the aqueous polymerdispersion which ultimately results. Irrespective of the amount ofemulsifier used it is possible to employ the protective colloids inamounts of up to 50% by weight—for example, in amounts of from 1 to 30%by weight based on the monomers.

As costabilizers as hydrophobic additive it is possible to admix themonomers with substances having a water solubility of less than 5×10⁻⁵,preferably 5×10⁻⁷ g/l in amounts of from 0.01% by weight to 10% byweight, preferably 0.1-1% by weight. Examples are hydrocarbons such ashexadecane, halogenated hydrocarbons, silanes, siloxanes, hydrophobicoils (olive oil), dyes, etc. In their stead it is also possible forblocked polyisocyanates to take on the function of the hydrophobe.

The reaction is preferably conducted in the presence of a catalyst.

In one preferred version first of all a mixture is prepared from themonomers, emulsifiers and/or protective colloids, and also, ifappropriate, hydrophobic additive and water. Then an emulsion isproduced and is heated with stirring. After the required reactiontemperature has been reached the catalyst is added via the water phase.Particular preference is given to adding a hydrophobic catalyst via thewater phase. The water solubility of the hydrophobic catalyst ispreferably ≦1 g/l.

Naturally, however, the catalyst can also be added to the oil phase ofthe emulsion, i.e., to the monomer phase, before dispersion is carriedbut, or can be added to the water phase immediately after the emulsionhas been prepared. Subsequently heating is carried out with stirring.

Suitable catalysts include in principle all those catalysts which arecommonly used in polyurethane chemistry.

These are, for example, organic amines, especially tertiary aliphatic,cycloaliphatic or aromatic amines, and/or Lewis-acidic organometalliccompounds. Examples of suitable Lewis-acidic organometallic compoundsinclude tin compounds, such as tin(II) salts of organic carboxylicacids, e.g., tin(II) acetate, tin(II) octoate, tin(II) ethylhexoate, andtin(II) laurate, and the dialkyltin(IV) salts of organic carboxylicacids, e.g., dimethyltin diacetate, dibutyltin diacetate, dibutyltindibutyrate, dibutyltin bis(2-ethylhexanoate), dibutyltin dilaurate,dibutyltin maleate, dioctyltin dilaurate, and dioctyltin diacetate.Metal complexes are also possible, such as acetylacetonates of iron, oftitanium, of aluminum, of zirconium, of manganese, of nickel, and ofcobalt. Further metal catalysts are described by Blank et al. inProgress in Organic Coatings, 1999, Vol. 35, pages 19-29.

Preferred Lewis-acidic organometallic compounds are dimethyltindiacetate, dibutyltin dibutyrate, dibutyltin bis(2-ethylhexanoate),dibutyltin dilaurate, diocyttin dilaurate, zirconium acetylacetonate andzirconium 2,2,6,6-tetramethyl-3,5-heptanedionate.

Bismuth and cobalt catalysts as well, and also cesium salts, can be usedas hydrophobic catalysts. Suitable cesium salts include those compoundsin which the following anions are employed: F⁻, Cl⁻, ClO⁻, ClO₃ ⁻, ClO₄⁻, Br⁻, I⁻, IO₃ ⁻, CN⁻, OCN⁻, NO₂ ⁻, NO₃ ⁻, HCO₃ ⁻, CO₃ ²⁻, S²⁻, SH⁻,HSO₃ ⁻, SO₃ ²⁻, HSO₄ ⁻, SO₄ ²⁻, S₂O₂ ²⁻, S₂O₄ ²⁻, S₂O₅ ²⁻, S₂O₆ ²⁻, S₂O₇²⁻, S₂O₈ ²⁻, H₂PO₂ ⁻, H₂PO₄ ⁻, HPO₄ ²⁻, PO₄ ³⁻, P₂O₇ ⁴⁻,(OC_(n)H_(2n+1))⁻, (C_(n)H_(2n−1)O₂)⁻, (C_(n)H_(2n−3)O₂)⁻, and(C_(n+1)H_(2n−2)O₄)²⁻, where n stands for numbers from 1 to 20.

Preference here is given to cesium carboxylates in which the anionconforms to the formulae (C_(n)H_(2n−1)O₂)⁻ and (C_(n+1)H_(2n−2)O₄)²⁻,with n being from 1 to 20. Particularly preferred cesium salts havemonocarboxylate anions of the general formula (C_(n)H_(2n−1)O₂)⁻where nstands for the numbers from 1 to 20. Particular mention may be made inthis context of the formate, acetate, propionate, hexanoate, and2-ethylhexanoate.

Examples that may be mentioned of customary organic amines include thefollowing: triethylamine, 1,4-diazabicyclo[2.2.2]octane, tributylamine,dimethylbenzylamine, N,N,N′,N′-tetramethylethylenediamine,N,N,N′,N′-tetramethylbutanediamine,N,N,N′,N′-tetramethylhexane-1,6-diamine, dimethylcyclohexylamine,dimethyidodecylamine, pentamethyldipropylenetriamine,pentamethyldiethylenetriamine, 3-methyl-6-dimethylamino-3-azapentol,dimethylaminopropylamine, 1,3-bisdimethylaminobutane,bis(2-dimethylaminoethyl) ether, N-ethylmorpholine, N-methylmorpholine,N-cyclohexylmorpholine, 2-dimethylaminoethoxyethanol,dimethylethanolamine, tetramethylhexamethylenediamine,dimethylamino-N-methylethanolamine, N-methylimidazole,N-formyl-N,N′-dimethylbutylenediamine, N-dimethylaminoethylmorpholine,3,3′-bisdimethylamino-di-n-propylamine and/or 2,2′-dipiparazinediisopropyl ether, dimethylpiparazine,tris(N,N-dimethylaminopropyl)-s-hexahydrotriazine, imidazoles such as1,2-dimethylimidazole,4-chloro-2,5-dimethyl-1-(N-methylaminoethyl)imidazole,2-aminopropyl-4,5-dimethoxy-1-methylimidazole,1-aminopropyl-2,4,5-tributylimidazole, 1-aminoethyl-4-hexylimidazole,1-aminobutyl-2,5-dimethylimidazole,1-(3-aminopropyl)-2-ethyl-4-methylimidazole, 1-(3-aminopropyl)imidazoleand/or 1-(3-aminopropyl)-2-methylimidazole.

Preferred organic amines are trialkylamines having independently of oneanother two C₁ to C₄ alkyl radicals and one alkyl or cycloalkyl radicalhaving 4 to 20 carbon atoms, examples being dimethyl-C₄-C₁₅-alkylaminesuch as dimethyidodecylamine or dimethyl-C₃-C₈-cycloalkylamine. Likewisepreferred organic amines are bicyclic amines which may if appropriatecomprise a further heteroatom such as oxygen or nitrogen, an examplebeing 1,4-diazabicyclo[2.2.2]octane.

Naturally it is also possible to use mixtures of two or more saidcompounds as catalysts.

The catalysts are used preferably in an amount of from 0.0001 to 10% byweight, more preferably in an amount of from 0.001 to 5% by weight,based on the total amount of the monomers used.

The polyurethane dispersions can comprise commercially customaryauxiliaries and additives such as blowing agents, defoamers,emulsifiers, thickeners, crosslinkers, fillers, thixotropic agents,colorants such as dyes and pigments, antioxidants, oxidation inhibitors,stabilizers, activators (accelerators), devolatilizers, luster agents,antistats, flame retardants, leveling assistants, binders, antifoams,fragrances, surfactants, viscosity modifiers, plasticizers, tackifierresins, chelating agents or compatibilizers.

The dispersion of the invention is used for producing aqueous coatingmaterials, adhesives, and sealants, for example, for coating wood, woodveneer, paper, board, card, textile, leather, nonwoven, plasticssurfaces, glass, ceramic, mineral building materials or metals,including coated metals. It can also be used to produce films or sheetsand also for impregnating, say, textiles or leather, as dispersants andpigment grinding compositions, as primers and adhesion promoters, ashydrophobicizers, and also as a laundry detergent additive and as anadditive to cosmetic formulations. It is also possible for thedispersions of the invention to be used for producing moldings orhydrogels, e.g., for optical lenses.

The dispersions of the invention can be used, further, as seed in theimplementation of a seed polymerization. For this the dispersions of theinvention can, for example, be emulsified and reacted in a reactor andthen the polymerization for which the dispersions of the invention serveas seed (in situ seed) can be conducted. The dispersions of theinvention can of course also be prepared separately and introduced intoa reactor, and the seed polymerization then initiated. Implementing suchseed polymerizations is known to a person skilled in the art and isdescribed for example in Baumstark and Schwartz, Dispersionen fürBautenfarben, Vincentz Verlag 2001 p.42 and Encyclopedia of polymerscience and technology, plastics, resins, rubbers fibers, Vol 5, J.Wiley and Sons, New York 1966, page 847.

The seed polymerization is preferably conducted as described in U.S.Pat. No. 5,189,107 col. 2 l.29 to col 9 l.55 or in WO 97/12921 from p.3l.19 and preferably as described therein at p.22 l.9 to p.23 l.8. Thedisclosure content of both these documents is hereby incorporated by wayof reference into the present description.

The invention is described in more detail below with reference toexamples.

Ppm and percentage figures used in this text, unless indicatedotherwise, are by weight.

EXAMPLES Example 1

9.5 g of a block copolymer of propylene oxide (PO) and ethylene oxide(EO) (terminal) with 21.3% by weight EO and an OH number to DIN 53240(OHN) of 26.7 mg KOH/g are mixed with 1.07 g of 3-methylpentane-1,5-dioland 2.5 g of isophorone diisocyanate (IPDI). The oil phase is stirredinto 28.8 g of fully demineralized (DI) water containing 3.4 g ofSteinapol NLS in 15% form from Goldschmidt REWO GmbH using a magneticstirrer at 750 rpm. After 10 minutes the mixture is homogeneous. Theemulsion is heated to 50° C. and 2 drops of dibutyltin dilaurate (DBTL)are added. After 5 hours it is filtered through a 40 μm filter and thesolids content is found to be 28.8%. The particle size is 35.5 nm.

Example 2

8.7 g of a block copolymer of PO and EO (terminal) with 13% by weight EOand an OHN of 35.2 mg KOH/g are mixed with 1.29 g of3-methylpentane-1,5-diol and 3 g of IPDI. The oil phase is stirred into28.7 g of DI water containing 3.4 g of Steinapol NLS in 15% form. After10 minutes the mixture is homogeneous. The emulsion is heated at 50° C.and 2 drops of DBTL are added. After 5 h it is filtered through a 40 μmfilter and the solids content is found to be 28.1%. The particle size is45.8 nm.

Example 3

12 g of a block copolymer of PO and EO (terminal) with 21.3% by weightEO and an OHN of 26.7 mg KOH/g are mixed with 0.13 g of butane-1,4-dioland 1.07 g of 4,4′-/2,4′-methylenedi(phenyl isocyanate) (MDI). The oilphase is stirred into 29 g of DI water containing 3.5 g of Steinapol NLSin 15% form. After 10 minutes the mixture is homogeneous. The emulsionis heated at 50° C. and 2 drops of DBTL are added. After 5 h it isfiltered through a 40 μm filter and the solids content is found to be28.1%. The particle size is 156 nm.

Example 4

7 g of a block copolymer of PO and EO (terminal) with 18.6% by weight EOand an OHN of 55.2 mg KOH/g are mixed with 1.6 g of3-methylpentane-1,5-diol, 0.31 g of hexadecane and 3.8 g of IPDI. Theoil phase is stirred into 28.1 g of DI water containing 3.3 g ofSteinapol NLS in 15% form. After 10 minutes the mixture is homogeneous.The emulsion is heated at 60° C. and 2 drops of K-Kat XC-6212 from KingIndustries are added. After 5 h it is filtered through a 40 μm filterand the solids content is found to be 28.2. The particle size is 31.2nm.

Example 5 Preparation of a polyesterdiol

328.7 g of isophthalic acid, 1003.4 g of adipic acid, 351.7 g ofneopentyl glycol, 605.5 g of hexane-1,6-diol and 1024.5 g ofpolyethylene glycol 400 are weighed out into a vessel, melted andreacted at a maximum temperature of 232° C. until the acid number is 5.5mg/g. The material is drained off at 80° C.

Acid number: 5.11 mg KOH/g to DIN 53402

OH number: 87.7 mg KOH/g to DIN 53240

Example 6

25.7 g of the polyesterdiol from Example 5 are mixed with 3.6 g ofbutane-1,4-diol and 13.4 g of IPDI. The oil phase is stirred into 97 gof DI water containing 5.7 g of Steinapol NLS in 15% form. After 10minutes the mixture is homogeneous. The emulsion is heated to 60° C. and6 drops of DBTL are added. After 5 h it is filtered through a 40μ filterand the solids content is found to be 27%. The particle size is 65.6 nm.

Example 7

9.6 g of a block copolymer of PO and EO (terminal) with 21.3% by weightEO and an OHN of 26.7 mg KOH/g are mixed with 0.95 g of neopentyl glycoland 2.54 g of IPDI. The oil phase is stirred into 28.8 g of DI watercontaining 3.5 g of Steinapol NLS in 15% form. After 10 minutes themixture is homogeneous. The emulsion is heated at 50° C. and 2 drops ofDBTL are added. After 5 h it is filtered through a 40 μm filter and thesolids content is found to be 26.9%. The particle size is 76.7 nm.

Example 8

8.7 g of a block copolymer of PO and EO (terminal) with 13% by weight EOand an OHN of 35.2 mg KOH/g are mixed with 1.14 g of neopentyl glycoland 3 g of IPDI. The oil phase is stirred into 28.3 g of DI watercontaining 3.4 g of Steinapol NLS in 15% form. After 10 minutes themixture is homogeneous. The emulsion is heated at 50° C. and 2 drops ofDBTL are added. After 5 h it is filtered through a 40 μm filter and thesolids content is found to be 27.3%. The particle size is 50.2 nm.

1. An aqueous primary dispersion comprising at least one polyurethaneobtainable by reacting a) at least one polyisocyanate, b1) at least onepolyol containing the structural unit —[—CH₂—CH₂]— one or more times,the structural unit —[—CH₂—CH₂—O]— deriving from a synthesis componentselected from the group comprising ethylene glycol, polyethylene glycolhaving a molar mass of between 106 and 2000, and ethylene oxide, b2) ifappropriate at least one polyol other than b1), b3) if appropriate atleast one compound containing at least two isocyanate-reactive groupsselected from thiol groups and primary and secondary amino groups, b4)if appropriate at least one monofunctional monomer having anisocyanate-reactive group, and c) if appropriate at least one ionic orpotentially ionic synthesis component, wherein the fraction of thestructural units —[—CH₂—CH₂]—, calculated at 44 g/mol, in the polyol b1)is from 10 to 90% by weight and the fraction of the structural units—[—CH₂—CH₂—O—]—, calculated at 44 g/mol, in the sum of the componentsa)+b1)+b2)+b3)+b4)+c) is at least 3% by weight.
 2. The primarydispersion according to claim 1, wherein the molecular weight of thepolyol b1) is at least 500 g/mol.
 3. The primary dispersion according toclaim 1, wherein the polyol b1) is a copolymer comprising ethylene oxideand propylene oxide.
 4. The primary dispersion according to claim 3,wherein the copolymer is a block copolymer.
 5. The primary dispersionaccording to claim 1, wherein the polyol b1) includes at least oneterminal structural unit —CH₂—O—H.
 6. The primary dispersion accordingto claim 1, wherein the polyol b1) is a polyesterol.
 7. The primarydispersion according to claim 1, wherein the average particle size asmeasured by dynamic light scattering using the Malvern® Autosizer 2 C isbelow 100 nm.
 8. A process for preparing a primary dispersion accordingto claim 1, which comprises reacting components a), b 1), if appropriateb2), if appropriate b3), and if appropriate b4) in the presence ofwater.
 9. The process for preparing a primary dispersion according toclaim 1, wherein dispersing takes place with shear forces below 10⁸W/cm³.
 10. A method of coating a substrate comprising applying theaqueous primary dispersion of claim 1 to the substrate thereby coatingthe substrate.
 11. The method of claim 10, wherein the substratecomprises a material selected from the group consisting of wood, woodveneer, paper, board, card, textile, leather, nonwoven, plastic, glass,ceramic, metals, coated metals, and mineral building materials.
 12. Theprimary dispersion according to claim 2, wherein the polyol b1) is acopolymer comprising ethylene oxide and propylene oxide.
 13. The primarydispersion according to claim 2, wherein the polyol b1) includes atleast one terminal structural unit —CH₂—O—H.
 14. The primary dispersionaccording to claim 3, wherein the polyol b1) includes at least oneterminal structural unit —CH₂—O—H.
 15. The primary dispersion accordingto claim 4, wherein the polyol b1) includes at least one terminalstructural unit —CH₂—O—H.
 16. The primary dispersion according to claim2, wherein the polyol b1) is a polyesterol.
 17. The primary dispersionaccording to claim 2, wherein the average particle size as measured bydynamic light scattering using the Malvern® Autosizer 2 C is below 100nm.
 18. The primary dispersion according to claim 3, wherein the averageparticle size as measured by dynamic light scattering using the Malvern®Autosizer 2 C is below 100 nm.
 19. The primary dispersion according toclaim 4, wherein the average particle size as measured by dynamic lightscattering using the Malvern® Autosizer 2 C is below 100 nm.
 20. Theprimary dispersion according to claim 5, wherein the average particlesize as measured by dynamic light scattering using the Malvern®Autosizer 2 C is below 100 nm.